Ok I purchased a truck and the check engine light has gone on please read on I really need help?

I purchased this vechile 6 days ago I have the pink slip and it was private party. My question I have heard I can get out of it because the man I bought it from did not preform the smog check is this true I realize that I can call the DMV tommorrow however I can not sleep he is telling me to get a lawer if I want him to fix this situation.