I Have A Sore In My Butt Crack. They Appear

I have a sore in my butt crack. They appear as three different sores in the same area. They are not painful an do not itch. I have them for less than a week and now have a swollen lymph node in my right groin. I have had a yeast infection recently but no other infections. I always practise safe sex. What could the cause of this be?