Since you will be seeing the vet in the morning or at some point today I would suggest against the aspirin because it may prevent them from using a safer alternative for 2 days after dosing the aspirin. Yes, you can give benedryl though. The dose is 1mg per pound. So, if your Chupa weighs 6lbs he can have 6mg or approximately 2.5ml of liquid benedryl.
Please let me know if further assistance is needed.