The nurse's notes in the medical record indicate the patient's pain was severe.

What is wrong with this sentence? Or wrong grammatical errors?

I see nothing wrong with it, unless there was more than one nurse making notes in the medical record.

There are no grammatical errors in the sentence. However, it would be more accurate to say "The nurse's notes in the medical record indicated that the patient's pain was severe" to indicate that the indication of severe pain was in the past.

The sentence "The nurse's notes in the medical record indicate the patient's pain was severe" does not contain any grammatical errors. However, it could be improved by adding an article before "patient's pain." The revised sentence would be: "The nurse's notes in the medical record indicate that the patient's pain was severe."