How did I get this planters wart?

I'm 13 and I have this annoying little planters wart on my left foot. I've heard that you can get it from sharing public bathing areas. But I haven't been to a public pool in years, and I only share a shower with my mom! anyway my mom said she had one as a teenager too and I was thinking it might be hereditary. well, if anyone has any clue where these things come from please tell me. It's really bothering me, and I gotta sc at it every night. Thanks for the info :)