If someone went to the hospital it could be more serious than a simple assault. Yes he could be arrested and taken to jail. Generally the first thing to do is call a bondsman and arrange to bail him out, then consult with an attorney in your area. Simple assault generally refers to a class C assault which is punishable by fine only. He can either be arrested or possibly just issued a citation. The bond is probably cheaper if it's a class c.
The best thing would be to get it all completed before you go to court. Every court is different with regard to how they treat probation violations so it is impossible to speculate on the outcome. Try talking to the lawyer who handled the case originally.