Girls Only Please!!!?

Ok so I'm going swimming tomorrow and I really want to go. I got my period last year and I have only had it three times, as it is super irregular. It just came up yesterday, and it's pretty heavy. I know you have to wear a tampon to go in the pool, but i've always worn pads and I really don't want to wear one. But the part thats worring me is this- when I went to try to insert a tampon (just to try it out) i couldn't get it in. I washed my hands and then (sorry about the details) pulled back the skin and peked in there. I only saw one holish thing, and I knew it was my vagina. But I took a closer look and There was like a huge lumpy, fleshy, misshapen thing that was partially blocking the entrance. it dosent hurt and I get my periods fine. No other symptoms.So anyways I tried to get the tampon in the smaller part that wasn't closed off, and it really really hurt. I'm kinda uncomfortable touching myself there too, so it felt super weird and painful. I tried a couple of times, relaxed, did all of the teqniques but it still wouln't/ i just out on a pad and threw the tampon away. First of all, what do you think I should do in the tampon department?? I don't want to have to miss swimming time once a month. And do you think this lump is serious?? I dont think it is because it dosent hurt, no discharge, and from what I know it's always been there because this is the first time ive taken a look. I cant go to a doctor (rather not go into that) so please help???