boxes

Ok so a month ago I changed to comic sans ms for fun but it had a problem with Hebrew so I changed back to Segoe UI and now I have a problem of some text showing as squares like: the time play button in Groove music checkbox and some other stuff I tried the control panel thing it didn't help...

I turned on my PC this morning and it seems like my computer language turned into some weird boxes and other hieroglyphics. This only affects my computer and not any other applications. I took a screenshot of my PC to give you an example of what it looks like, unfortunately, I can't post it in...

I let my nephew play with my computer he ended up putting two weird boxes in the middle of the screen i cant get it out pls help. i attached a picture of what it looks like. your help is greatly appreciated!