what is this?

Arye • 6-24-16 😜👅

Idk how I got this?? I got it a couple days ago, and when I noticed it it felt like a burn like I burned myself? But I didn't. I don't even remember burning myself? I showed my bf and he said what if it's from me tanning? {I go to the tanning bed}  he said his uncle had something like that but it was worse and it ended up being skin cancer or something from the tanning bed but it was much worse.. I looked up pictures and mine don't even look bad at all compared to those pictures.. I mean I went tanning yesterday and it didn't get any worse.. I need help.