I have a weird bump inside my vagina. Not too far in but I think it's near the cervix too.?

Hi I have a really weird bump inside my vagina. It's as big as a cherry but it's flat and kinda soft/hard. Right when I stick my finger in, to check it, I can feel it. My boyfriend accidentally ejaculated in me but six hours later i took plan b. After that, things have been happening. Is it tellin me that I'm pregnant? I really need help. I took pregnancy tests but they're negative. My vagina becomes very tight then it's back to normal again. I need major help. I'm scared. Idk wat it is. Respond asap.