Which kind of pain should you Work Through?

[ExTravaGanzA]

An hour or two ago I slammed the lower back part of my pelvis against a cement wall, the pain is not excruciating but I can feel it and it feels like I bruised the bone a bit, feels swolen too.

Would it be ok to work through the pain of an injury such as this? I have a Muay Thai class tonight and before that I was planning on heading to the Gym.