You could get arrested because the police may not be able to determine exactly who was at fault or what exactly happened at the time o the incident. But the likelihood of your being convicted would be slim if you were truly defending yourself. Also, it is important to know the law in your state regarding weapons because some states have weapons licenses that include mace, and it is illegal to carry without the proper license.
Is the guy still living in your dumpster?
this is a messy case, you should contact a lawyer.