About 3 or 4 months ago I started teaching myself to play steel string acoustic guitar using free online lessons. Because I am not working with a tutor in person, I have to be more careful about developing bad habits.
Obviously beginners will have pain in the tips of their fingers as callouses are developed, but recently after starting to practice more often, the middle knuckle on the index finger of my fretting hand has started to feel sore. It feels almost like it is bruised and there is light soreness if I curl the finger closed. It does not appear to be swollen and I don't feel anything if I just leave it extended, but I am worried my technique may be off, because I am 19, and I didn't think I would experience this. My other knuckles feel fine. I just don't want to play through it if I am hurting my hands.
I believe it is from playing chords like Dm and C where the first finger has to press fairly hard, and for the C chord where the knuckle has to be at an angle in order to get a clean note. I was also starting to attempt to play the F bar chord (trying for 5 min or so a day) which definitely strains the first finger I would think.
I also have never had my guitar setup, I am having it setup now while waiting for the soreness to go away in hopes it will be easier to play. It is a $200 level Fender so the action shouldn't be that bad, but it was mail ordered and I think it has a fairly high action for a beginner (about 3mm at 12 fret of low E).
Until recently I was practicing 45 minutes to and hour a day straight (6 days a week), but recently I had been playing or practicing for closer to an hour and a half and possibly more from all the times I pick it up during the day and play for 10 minutes.
Is it normal for beginners to have sore knuckles or should I be concerned my technique is off?