That appears to be an impact damage to the (protective ) plastic frame. You should inspect the inside of the tank and look for cracks in the glass to determine if you have a problem that is going to get worse, or not.
I would guess that the plastic absorbed the damage, and that the glass is OK or else you probably would have had a leak /seep in the corner coming out from that area (vs dripping down from above from recent water change) before now.
Also, those trim pieces at the bottom are not as important structurally as the silicone seal inside for keeping the tank together. The cracked plastic is not anything to worry about as causing a future tank failure. Cracked glass would be, so check if you can. No crack and you should have no worries.