It is not a question of being at MMI. The doctor has to come up with some estimate of your percentage of impairment and/or loss of wage earning capacity and explain why he has the opinion that he has. For example, let's say that he opines that you have a 2% whole body loss or 10% loss of use of your leg. Those percentages might translate into some kind of lump sum award.
Some states would only award a lump sum if you had a loss of wage earning capacity. I don't know the specific rule in NJ, but the fact that you returned to full duty (and presumably at same pay) with your date of injury employer, might work against you if that is the rule in your state.
It can't hurt to have a consultation with a local WC attorney. Most of the time, any attorney fee is either paid by the carrier or deducted from your award. Ergo, it is unlikely that you would have to come up with any money out of pocket solely for an initial consultation.
Since much of this stuff really is state specific, you might want to consult a local WC attorney for guidance. I don't believe that any follow these boards.