['I had made a bad mistake on a work project, and my coworker took the blame for it. I felt bad for not speaking up to my boss.', 'That really sucks. Did you make it up to your co-worker?', 'I apologized to them later about it. It was tough hearing our boss scolding them about it though.']
That's good to hear that you and your co-worker mad amends. Live and learn!
I feel really bad that my coworker took the blame for something I messed up on. I should have spoken up when our boss was scolding them about it.