It's actually perfectly normal, it's all part of the healing process (: just wash your mouth out with alcohol free mouthwash about twice a day, and you'll find the swelling goes down soon :)
Could be cold sores, canker sores or blisters.
...but its probably, (hopefully!), Fordyce's condition, which affects 50-90% of men. And which is a gigantic range for an estimate!...