as for the DL, it is not uncommon to be sore when you do something for the first time.  try to loosen it up with some work on the low back and glutes. if you are feeling pain, then you should go to see a clinician.

over time adaptation will occur. however, with the DL, low back soreness can also mean that you are not using your glutes enough and your low back is compensating by overworking. you may also see problems in your hamstrings. 

you’d also want to examine your bracing and posture during the DL and make sure you are remaining in good position the whole way.

last, you will want to make sure you are hinging at the hip properly. if this is your first time with the DL, i would find a good coach to check you out on your form so that your low back soreness doesn’t develop into something more serious.

search ‘deadlift’ for a bunch of videos available here in mobilitywod.com on the performing the DL safely and properly.