can I sue

I'm sure that there is quite a bit more information, that you haven't (quite properly) included in your question.  For reliable advice, you need to have a lawyer take a look at all the facts.  One place that you can look for a qualified attorney near you is our website, http://attorneypages.com

In most cases, a lawsuit isn't the first thing to try, because it usually takes much too long.  There are procedures to get what is usually called a temporary injunction, a court order that gives some protection shortly after the case is filed, but it's not often granted and it's usually expensive to ask for.  Your lawyer will probably start with a nasty letter -- and a lawyer's nasty letter is likely to be better than yours for two reasons:  one is that a lawyer knows what is more likely to hit home, and the other is that a lawyer is more likely to be taken seriously, on your behalf.