Onions narrowly missed out on selection for the ongoing fourth Test on his home ground and now faces a struggle to retain his place in the squad when the sides meet in the series finale at The Oval on August 21.
He broke the little finger of his right hand attempting to claim a caught and bowled against Scotland in Sunday's ECB 40 clash.
A Durham statement read: "Graham Onions has been ruled out of Durham's ECB fixtures this week after he suffered a broken finger in yesterday's match against Scotland.
"Onions has a break in his little finger on his right hand in his knuckle joint which was sustained in an attempt to catch the ball off his own bowling.
"At this stage Onions is hoping to be fit to play in Durham's next County Championship match against Surrey commencing on Thursday August 22nd."
The seamer tweeted: "How's my luck?! Unfortunately yesterday I broke my little pinky dropping a catch off my own bowling so I won't be travelling today."