What Should I Do?

4 years ago, we had a family get-together were all my relatives and cousins had come for a fair.

One of my cousin sister same age as me whom I was close to from a young age was also there. Me, an 15yo adolescent had a weird reaction when I met her. She had developed into a girl with huge tits and a fat ass.

In the middle of the night, I could not control my urges and went next to her. Slowly feeling her growing tits and smoot tummy. Pressing my hard penis on her ass and spooning her. I think she knew what I was doing but she kept quite. I grew bolder and pressed her tits even harder so that she twiched. I stopped there and went back to sleep.

We have grown distant over the years but still have a friendly relation. But I feel guilty as hell for doing something like that. I don't know what to do. We are 19 now and I think what I did may have been due adolescents hormones or curiosity and my urges but that reason cannot undo what I did. What do I do?