I am new to BitcoinTalk and when I registered, I was blocked and it had said I couldn't register a user, because apparently Satoshi was a reserved name.
What exact error message did you get, AFAIK, there is no block on any username, except it has previously been used by someone else
it's likely someone tried to use that name already on the forum, hence you needed to find another variation of it.
Your current username is fine, but to avoid issues of impersonation, you could request a user to give you a neutral feedback on your profile, stating that you have no ties to the pseudonym
satoshi, using this thread as a reference.