You can continue to contribute. You can claim tax relief for the payments in future tax years. You will be limited to your age related maximum tax relief in those future years , so when you include the backdated contributions you will be restricted in the amount you can contribute in those future years.
If you have a surplus of money at present that you want to invest, this can be a good idea as you will be gaining tax free gains on a larger amount in your pension for a longer time scale