Depending on the laws of your state, city, or county you are not allowed, legally speaking, to go after someone, even if they have assaulted you, if there is no eminent threat to you safety. Further more if you can avoid it you have to; meaning that if you specifically engage someone and you had the opportunity to avoid them it is you that is at fault.
Disclaimer: IANAL, but I dated one who specialized in this, so I got an earful on more than one occasion. This is called the "duty to retreat", and while it is generally true that in most situations you have a duty to retreat if you can
and if a reasonable person, placed in your situation, would not feel threatened. There are numerous exceptions, however. For example, since we're making generalizations, it's generally not
the case that you have a duty to retreat within your own home, if your attacker does not also live there.
(btw, it's "imminent")