On health grounds watermelon should be eaten immediately after it is cut. Nt to keep in fridge. N if texture is changed the taste will be changed too. So betr throw this time n be careful next time.
I dont know abt the water melon if it cut which we ask seller to cut for taste.But yes i had the watermelon which was lying more then a week in fridge it tasted good and some part was little discolred so i throw it away.So u can have it.Cut the rotten part.