What did you use to cut your fabric? I find that exacto-type knives cause more of a "groove" in the mat than most rotary cutters. Also are you pressing too hard if you are using a rotary cutter? Perhaps a change of blade is in order if this is the case.
Washing your mat with mild detergent and a plastic scrubby should be all the "care" you need for your Olfa mat.
Jan in VA