You'll get worthless seeds in that plant and if it's near other plants and there is wind they could get seeded as well. However, many times you won't get seeds anywhere except right at that site. To be safe you should separate it from the others and just finish the grow. The smoke will still be good and you'll get a nice firecracker every once in a while to keep you on your toes. It's not that big a deal.
Moving forward you want to make sure that you didn't do anything that stressed the plant and caused it to hermit. No light leaks are the big one.