Anal blood. Once a day most of the time.

Hi! Last night I was tickling my anus with a finger (just for pure fun, not itching or something) and I decided to try to put my finger in it. But I think I failed becuase I didn't really find the hole to plug in. At least I don't think my finger got in anything. In other words, I may just tickling around my anus. However, this morning when I pooped, the tissue had some bright red blood on it, not much though,approx the half of the first knuckle of the forefinger. And it appears on the left side of the poop on the tissue. It may be psychological effect, but I occasionally felt my anus a little bit painful today. I am very worried that it may be cancer or something, if it's not because of my finger(cause I don't think I plugged in!). Btw I am 17 female and poop once a day most of the time. Thank you.