I have trouble with my stutter when I get nervous or excited but my timing was a bit different I got stuck on the word cock so what came out was the noise "bawk bawk bawk" before I coild stop myself.

It was probably 15 years ago but it still haunts me.

Hydrogen peroxide will remove the blood but also may bleach your pants. Start with with water and a brush to get get off as much as possible, then use the hydrogen peroxide.