First off, always shave downward, or "with the grain" your hair grows at an angle, and you want to follow that angle. As far as the bumps go, wash them with rubbing alcohol amd put some lotion on them. They should clear up with time.
The small red bumps are probably your hairs trying to grow back. As for the puss, if the razor has been used before it could of transmitted an infection. But shaving also exposes the hair roots so that could easily contract an infection.:/