It is aways possible that he has damaged the trachea when he choked himself.
Please do not use aloe ,this is actually toxic to dogs and can cause vomiting diarrhea, depression, tremors, and change in urine color.
Read more here
Milk is also not recommend, dogs are lactose intolerant so this too can cause vomiting, diarrhea and nausea.Nausea can lead to gagging.
If you have Pepcid AC this will help calm the stomach if this is increasing the gagging
Here is a link to the use of and dosing for this medication.
You can give some warm water or chicken broth with a small amount of honey to sooth the throat.
You also want to moisten the dog food if he eats dry kibble.
If he is still gagging tomorrow I would suggest having your vet take a look just to be sure he has not caused damage to the trachea.There may be internal swelling that you can not see , your vet will be able to give medication if needed.
I hope he does ok,please reply back if you have additional questions or concerns.
Edited by Candy on 1/11/2011 at 12:51 AM EST