I encountered a similar problem when starting.
Modified the newbie routine so that I do only jelqs + just a few second stretch’s in all directions with low intensity.
After about a week of PE, my unit became harder and more conditioned to implement 5 minutes of stretching in my routine.
BTW to answer your question, I myself gained about .3” in 12 days in length - which means, besides the fact that I gain well, that you CAN develop more length by just doing jelqs.
My advice: try it like I did. Do small stretches to make your unit more used to the stress of stretches. Just, don’t force it while it still hurts.