Backup all your Personal Data to external media if you haven't already done so, and use W10 System Restore to "roll-back" your system to a point in time before that happened to your machine.
BTW, did your computer come with W10 pre-loaded from the factory? Or did you upgrade from an earlier windows version such as W7/W8x?
With weekly and monthly push-updates coming in from MS, you need to make sure you check your computer frequently, at least once a week to see if anything is wrong with it.
Also, there are viruses that cause this kind of damage to the Default Programs applet; we suggest you scan for viruses/malware with your built-in AV scanner. Scan/remove all viruses found. Next, download the free MALWAREBYTES...