Backwash instead of drain during vacuum

[Holzer]

Just did a stupid move, didnt read the label close and I did the backwash on the filter instead of the direct drain as I was vacuuming a bunch of leaves and crap off the bottom of the pool. The presure went up on the filter and the volume of water going out went way down. Did I mess something up or will this fix itself. Do I need to open the filter and pull all the sand out ?
Cheers
Ron