The 27-year-old was attacked at around 1am by at least one other male inside a Letterkenny nightclub.
His injuries are not life threatening, but the man remains in Letterkenny General Hospital this afternoon.
Gardai say they are following a line of enquiry.
Meanwhile in a separate incident outside the nightclub a man had a glass bottle smashed in his face.
He was taken to the Emergency Department at Letterkenny General where he received a number of stitches to his face.
He was released from hospital in the early hours of this morning.
Gardai are appealing for witnesses to come forward.