Small holes in cotton clothing often result from snagging or destructive moths and insects that eat tiny holes into the clothing typically no bigger than a pellet. Small holes are easy to mend and unnoticeable after repairs. Larger holes are more noticeable, but there are ways to hide the larger holes so that you do not have to throw out a favorite cotton garment over one or two small holes.
Take the garment you are mending with you to purchase a spool of cotton thread that is the exact same color as the garment or that spot on the garment. For a broader selection of threading, visit a crafting, hobby or sewing supply store.
Unfold and stretch out the piece before securing the thread once the hole is mended; this ensures that the cotton does not pucker around the mended spots. Pull the threaded needle underneath the previous stitches then cut off the excess string and repeat the entire process on another small hole.