Men: Ever had a small bump on your head?

My husband has a small red bump on his head, normally I wouldn't be concerned because people get pimples and stuff but we both found it very odd for a bump to be on the head of his . Pimples are causde from clogged hair follicles...obviously there isn't any here there! So has anyone ever had one of these before? I am with him almost 24/7 so I doubt that it could be an std, and if it was...wouldnt there be more than just one little bump?