take a break; get away from social and sensory input as fast as you can and retreat into yourself.
if you cant go home just yet, for whatever reason, i recommend going to the toilet for a bit. take a cubicle and just sit there for a few minutes untill you feel better, noone will think of that as weird; everyone goes to the toilet on occasion, and when you are there, noone tries to talk to someone else (well, not on a mans toilet at least)