Can you get an infection from getting hit in the leg?

I was playing soccer with my cousins last weekend and one of my cousins got kicked in the shin. it turned into a huge bump but there was no scrape or breaking of skin at all. It's been almost a week and the bump on her shin is still there! Told me that the swelling hasn't gone whatsoever and that it's still soar. Her family went camping and noticed it and got worried it could be an infection. I always though that infection was caused by bacteria.. so idk if it would be that. But does anyone know if this is possible.. or if it's something serious? Thanks for your help!