I don't think that the dried blood would cause an infection, but the wound might become infected if you don't take care of it properly. Following your doctors orders. When he says that that it it is safe to clean the area, do so carefully to help prevent infeciton. From what I have been told, it may be sensitive for a while. You may not be able to have sex/masturbate for up to a month depending on how it feels as these activites may create discomfort or pain.
Somewhere on the web, a read a diary that someone had written on their circumcision. That person was on bed rest, unable to do almost anything for about two weeks. I'll see if I can locate the link for you.
Good luck, and hopefully it will feel better soon!