can cause plywood to sag and fail etc.
At some point it should be repaired and depending on the age of the roof etc and if they can match shingles I would think it would be less than $1000 to fix it. (probably around 500)
If it's an older roof, you may want to bite the bullet and do the whole roof.
Insurance will likely not cover unless it was damaged by hail or a falling object etc.