In the meantime, you should also keep a close eye on his mucus membranes, capillary refill time and respiratory rate tonight as follows
Mucus membranes - flip his lip and look at the color of the gums. They should maintain a nice salmon pink color. Get your dog to the emergency Vet if they appeal white or very pale pink, or if they are a dark deep red color.
Capillary Refill time - this measures blood perfusion and test this by putting your thumb on his gum to apply pressure. After you release your thumb you will see the gum blanch. Capillary refill time is the amount of time it takes (in seconds) for the gum to return to a healthy pink color from the blanced white color. If 2 seconds or less don't worry - if it is taking significantly more time, again - off to the emergency Vet
Respiratory Rate - if he is continuously panting throughout the night this is a sign of shock and or pain and a signal for a trip to the emergency Vet.
As I say, I would personally avoid giving him any further aspirin at this stage and rather - just monitor his above signs and get his actual temperature. For more info on how to do this, please visit this site: http://www.petplace.com/dogs/how-to-take-your-dog-s-temperature/page1.aspx . If he seems lethargic, or has a high temperature then please be sure to get him checked out by your local ER Vet won't you.
If you have any further questions in the meantime, please be sure to ask.
Thank you for your question and please now click ACCEPT.
Dr M D Edwards