If it’s not too big some spackle and tape, sand and paint.
However, why has it cracked? Is there a leak, or just settling? Make sure there are no underlying issue you can see.
Judy gave a great answer. Often the same crack, though repaired, will continue to expand and contract with the change from summer to cooler weather. We had this issue in one of our homes in the past. In the summer couldn't see the crack we'd repaired, then when coder weather came it became colder weather again
If the house is plastered, not dry walled, The crack will keep returning
They make a tape that covers the crack even with the small expansion and shrinkage with weather. A handyman did it for me several years ago and I have not seen the crack since. Have to ask Lowes or Home Depot representatives what it is.
Little Cookie, You need to start with spackle, then sand it when it dries completelycompletely. Repaint. Aloha!
Thank you ALL! Wonderful advise that I will take right after the holidays!