Is it necessary to repeat the prayer, or only to correct the word, if a word was pronounced in prayer with a "dammah" or "fathah" instead of a "kasra"?

If a worshipper intentionally mispronounces a word, their prayer is invalid and must be repeated, because they have introduced an extraneous word into their prayer. However, if they did so out of forgetfulness, their prayer is valid, and it suffices for them to correct it if rectification is possible.