Matthew Stafford's wife, Kelly, is issuing a mea culpa ... saying she's truly sorry for calling an Instagram troll a "misogynistic pig" after he criticized her for not wearing makeup.

The troll left his rude comment under a photo of Kelly and her kids ... saying, "[Matthew] could have his pick of women so just a little bit of makeup."

"If you weren't married you'd have it on."

Kelly was so pissed about the hurtful words ... she clapped back and called him "a typical misogynistic pig," while also sarcastically wishing him a happy holiday on her IG story.