Chances are it did not hurt the battery but: it can, one cell will always be less efficient than some of the others. That cell can be permanently damaged by being reverse charged by the stronger cells as they continue to discharge. If that happens, you may never be able to get that cell to perform properly. The only way to know for sure is to charge the battery for 15 to 16 hours at a slow charge (0.1C) and then measure the capacity with a good cycler. It may take two or three cycles of slow charge/discharge to completely recover the battery's full capacity.