What to do when your turtle has a nose bleed?ASAP!?

My turtle just had a nose bleed in his tank! His nose is red, the water is slightly red, and the water is all foamy at the top. I did not rinse him in hot water or soap, I did not feed him yet, I did not drop him, he is not injured, and he did not eat any chemicals. What should I do!? Help ASAP!