I'm assuming this is the fitted sheet, since repairs aren't typically noticeable in the top sheet.
I've done it, but it all depends. If the tear is low on the sheet (near the feet), I always put the repaired end at the head of the bed because that puts it under the pillow where it is unnoticeable. It's also less noticeable to repair thicker sheets, like flannel. I do have one set of sheet for the kid that I mended that he won't use in summer. They are now "winter" sheets because he doesn't feel the repair when wearing sweats to sleep in, but feels it bare legged in the summer.
I've also turned king fitted sheets into twin top sheets by cutting off elastic and damage, then hemming. I've turned sheets into pillow cases as well.