A couple of things to look for. Has he broken the skin on his cheek? Could be apses developing.
Could it be insect bites?
Is he eating well or is there a problem? The problem could be inside the mouth.
Just noticed that the date of your post is 14th July - you have probably solved the problem already.
In the case of apses it is important to get treatment from the vet before the infection gets serious.
What has happened in your case?
Hopefully all is well.
Kate
