Someone got cut with a shared shaving stick with fresh blood on the blade. what's the hiv risk?

See previous replies. If you mean a razor, and if it had visible fresh (wet) blood, there might be small risk of infection. It's one of those theoretical risks that happens rarely if ever in real life. Just wiping the blade would probably eliminate all risk. Of course, you shouldn't be using a previously used razor unless disinfected first. But even without such precaution, virtually no risk.