I like my leather recliner sofa. It's in good shape except for one arm that separated from the frame! The reclining mechanism continues to work. Can we repair this or does it needs professional help?
It looks like the underside material that is holding the arm in place is torn or ripped.
The arm looks broken to me. You will need to have it fixed professionally.
Your DIY repair may depend on how it got separated from the frame.
You are lucky that the mechanism is still working so you may be able to have it repaired at a reasonable cost.