Turn the shirt inside out
Trim any loose threads around the hole
Thread a needle with matching thread
Tie a knot at the end of the thread
Bring the needle up from the inside of the shirt near the hole
Sew small stitches around the edge of the hole
Pull the thread snug after each stitch
Continue stitching until the hole is closed
Make a small knot on the inside to secure the thread
Trim the excess thread
Turn the shirt right side out
Press the repaired area flat if needed