Was the f-86 the first aircraft with a swept wing variation?

No. J.W. Dunne designed and built aircraft with swept wings in the first decade of the 20th century, but his designs weren't swept for the same reason as the F-86's. Aircraft speeds were not yet high enough to warrant sweep, so many different models of aircraft had swept wings (both back and forward!) for other reasons, such as controlling the aircraft's center of gravity (as on the XP-55 or Me-262) or to increase low-speed lift (Ju-287). But I assume you want to know what the first aircraft was which had swept wings to help it go faster. Research into sweeping wings to reduce supersonic drag was first seriously proposed by Dr. Adolf Busemann in 1935, and fellow German scientist Albert Betz immediately suggested that wing sweep would be equally useful for reducing drag in the transonic regime as well, this being the speed range in which aircraft like the F-86 Sabre and today's airliners fly. It appears that the first aircraft which had swept wings for high speed was the XP-86, which went on to become the F-86. The XP-86's first flight on Oct 1 1947 just beat the USAF's B-47 first flight on Dec 17 1947, and the MiG-15's first flight on Dec 30 1947.