Those are from concussions. There is a grading system for the severity of concussions from type 1 all the way up to perhaps type 4 but I forget. The effects become more severe depending on what kind of concussive blow you received. If I remember right type 2 or 3 symptoms include headaches.

I recommend that you look this information up. Concussions are always serious and the effects accumulate. If you're getting hit too much in sparring you must make alterations to your style. Its never OK to get hit. Not even once.