I know when a girl bumps into you generally it a huge IOI because its a mixture of both touch and proximity. Two surefire signs of attraction. But in a club atmosphere, I generally feel that its bound to happen here and there. Is it generally a sign to dance with them or start conversation?

Obviously excluding instances where there is no walking room, and body contact is inevitable on the dancefloor for example or a crowded room. But even then some girls seem to exaggerate the contact by rubbing their nipple on you or ass, or pressing their bodies into you instead of lightly grazing.