Legal Question in Business Law in California

You absolutely risk being sued, but how high that risk is depends on a LOT of details you don't provide. It also depends on what you mean by "register." Company names for Secretary of State incorporation or LLC registration can be nearly identical. The name by which you do business for trademark purposes cannot be too similar, but that also depends on the words and images used. So while you may be able to incorporate or form an LLC under a name by adding two words, you are getting into complicated and risky areas trying to do that as a trade name to do competing business in the same industry.