Does anyone know what these bumps are?

Hi everyone, We rescued our new friend here about a month ago and have been noticing these past few days increasing number of bumps on his head and neck. They don’t seem to be bothering him yet but I am unsure if this is something we should be worried about. If anyone’s pup has experienced this please let me know what the next steps are! Thank you guys in advance.

We believe he is a cane corso/ boxer mix about 3 years old. No known past medical history besides a pressure ulcer on his right hip. He was in the shelter for a little over a month prior to us taking him home.