You should definitely follow the advice of getting a legal counsel and dealing with the issue now as opposed to later.

Also, you should

1. Clear your thoughts around what you want for your company at this point in time, in the near future, and in the long run.

2. Understand what role you envision yourself and your fellow co-founder playing in the above scheme of things.

3. With thoughts around these two areas cleared up, you should sit and talk about this with your co-founder at the earliest.