Hurt my arm today, indentation in bicep, help?

i was boxing today, and after i finished i noticed my bicep had an indentation in the middle when i flexed, it doesn't hurt much, there is just a dull ache when i flex, otherwise it doesn't really bother me. the indent in my bicep kind of worries me though. any ideas what it is or how to fix it? it doesn't seem serious, i think it might just be a pulled or strained tendon or something along the lines of that. any ideas? thanks!