Kayal started feeling muscle pain in a session and was instantly sent for an MRI scan by Hoops manager Neil Lennon.
But the Israeli internationalist recovered well and scored a sensational goal in the 4-1 win over Dundee United at Parkhead on Sunday.
He said: "I was afraid I was finished for the season, but in the end it turned out all right.
"On Sunday, I arrived half an hour before everyone else and had to pass a fitness test. And I told the masseur I was going to score."
Kayal spent much of the first half of the season sitting on the sidelines.
He has thanked gaffer Lennon for keeping his spirits up when he was out of action before Christmas.
And he has vowed to repay him by helping Celtic land the SPL title and then the Scottish Cup.
He said: "It is not easy to settle abroad and I was also out for three months with an injury.
"When I wasn't playing, the manager spoke to me all the time and supported me.
"Since I have returned I have felt good every day and I want to be part of this team's success this season.
"To return to good form, which can be difficult, has been fun for me. My head is concentrating on the league and cup double."