I have a whitish and reddish bump on my lower left butt cheek, its hard and it hurts i think its from sitting on a public toilet seat.what should i do?

Pimple or boil: This sounds like a standard pimple or boil, a minor skin infection. It is unlikely caused by something caught on a toilet seat. As for any pimple or boil, just leave it alone; it should come to a head and drain on its own in a few days. If it gets a lot larger, if there is spreading redness around it, or if you develop a fever, see a doctor immediatley. If in doubt, contact your own doctor.