Dogs will bite if they are not properly food socialized. They are defending their food (even though this time it was garbage). One thing to keep in mind, dogs almost never bite by accident. They are crazy accurate with their teeth.
If they bite you, they intended to bite you. Therefore, they don't respect you or your sons superior place in the pack. This can become a very big problem with small dogs.
You have two problems here:
1. The dog gets in the trash
2. The dog bites when defending food
To stop the trash eating, fill an empty soda can with little rocks and tape the opening shut to create a noise bomb. Toss it at the dog when you see him nosing the trash container (you have a lid on the trash, right?). Set up the can so you can see it and even put some tempting stuff in there.
The noise, immediately by your strong "No!" will send the message. If that fails to work (you might need to do it a dozen times at least) take some mouse traps and set them on top of the trash. They won't hurt him, but will scare the crap of of him and he will relate this negative feedback to the trash can.
For biting, it's not as straight forward. You have had the dog a year and it had a year or so before you to learn bad habits.
Immediately institute a zero teeth on skin policy. No play biting. Zero contact between skin and teeth. When contact happens, smack him under the chin (not on the nose or head) with a sharp rap upward and say in a commanding voice "No bite".
Watch for him to become submissive and beg for forgiveness. At first ignore him. Wait about ten minutes and nonchalantly pet him (don't make a bid deal out of it - just reassure him you are the leader and he is still valued in the pack).
If the biting continues, look at why he is biting. Is it fear? Protection of food or toys? Aggression? dominance?
Fear is the hardest to break. In fact, a dog that fear bites will be a problem and probably should be euthanized. This is a mental issue they seldom overcome.
Protection of food and toys can be dealt with by using exposure techniques (taking away the toys and food and handling toys and food while they are using it) and using negative reinforcement in conjunction when they act out.
You must time your corrections precisely to the infraction. Waiting even 30 seconds won't connect the dog to the undesired behavior.
Aggression and dominance are issues that take leadership and consistency and usually a change in how you deal with the dog. This means:
Always enforce commands no matter how trivial. If I say "sit", you are going to sit.
Ignore the dog when you arrive (no greetings, no eye contact). Wait until the dog is calm to greet him ON YOUR TERMS.
Only pet and praise when the dog is in a calm state.
Don't let the dog enter or leave the house in front of you. You go first.
Make the dog sit and stay after putting his food bowl down. He only gets to et when you say it is OK.
Excersize the dog every day until he is tired.
Don't let him see you pick up his poop. (serious)
If the dog is clearly being aggressive, grab him by the back of his neck, shove him down on the floor and hold him until he changes to a relaxed, calm state. You will literally physically dominate him.
Last option, give him a smack down he won't forget if he continues to be aggressive towards you, your family or others. Hit him in the chin, shoulder area or rear thighs. Don't hit his stomach, neck, nose, etc.
Before everyone freaks out about that last recommendation, think about how roughly dogs handle this stuff in the pack. You won't have to do this more than once or twice to stop the behavior.
If the biting and aggression doesnt stop after four to six months of consistently doing the above, I'd put the dog down. Not worth getting your kids (or someone else's kids) fàce torn up.
PM If you want more advice.