The 23-year old forward struck with just over 20 minutes remaining to put 'Gers up 3-2 in the match at Ibrox they eventually won 4-2 and has since confessed that he thought he may never break his duck against the Hoops after missing two chances earlier in the contest.
"It was like a massive weight had been lifted from my shoulders," he said.
"I missed with a volley after I'd read (Badr) El Kaddouri's headed back-pass.
"I did everything right apart from the finish.
"I couldn't believe it - and at that moment I thought I'd never score against Celtic.
"Fortunately, I got another opportunity and I was able to keep my composure and make the most of it.
"My first attempt was blocked and when the ball came back to me I just concentrated on getting it to my left side and hitting it as hard as I could.
"It was sheer elation for me seeing it hit the net.
"I waited three years for the goal and when it came yesterday it was a mixture of relief and joy.
"Now I want many more goals against Celtic.
"I don't think I'll ever get close to the gaffer's record in Old Firm games - (Ally McCoist scored 27 times in 15 years).
"After getting my first I just want to keep on scoring against Celtic."