Contact with dry blood how worried should I be?

Was at martial arts last night and there was dried blood on one of the pads we punched.

My knuckles currently have the top layer of skin missing from hitting the pads without gloves a few days before. Have been using savalon on them a lot in the last few days. I haven't seen my knuckles bleed over the last day or two before I went they are just sore.

I think the blood was from someone in the group and had maybe dried for 15-20 minutes.

I did not realise you could get anything from dried blood until I googled when I got home.

I am worried that with the top part of the skin missing on my knuckles I might have gotten some disease from it? Or would my skin still protect me even though the top layer has gone?

Is the chance of getting something here low or high? Should I be worried about HIV , hep c and B?