Hi. Welcome to GT. Since you're brand new to playing guitar my first suggestion would be to continue with left hand fretting and see if that joint doesn't loosen up with use. Since you've never had to push it maybe just using it more will make it more flexible. Warm up your left hand before practicing with either a heating pad or running it under warm water for a minute or so. NEVER push it to where it hurts bad and stop when it starts to feel sore. All your fingers will be made to bend in ways they aren't used to but keep and eye on the bad finger since it has other issues.