How to get crisp clear photo?

I own nikon d5100. Yesterday i went on a concert, a night concert. The metering was not constant on any mode (matrix, center and spot).So i had to make my own judgements for taking pics the problem i faced was that some parts of photo were blurr. I mostly used 1/30 or 1/20 shutter speed on lowest aperture. I just want to know that how to avoid this blurryness without using flash and getting a bright crisp picture. this happened when i took photo

Added (1). I took this photo with 1/30 shutter speed and iso to 6400. However if i would have chosen 1/250th than the photo would've been underexposed.

Increase ISO to around 1600.It will be grainy but you should get more decent shots.

The shutter speed is your problem, assuming you are focusing correctly.
They recommend 1/250th of a second or faster for handheld unless you are very steady.
Increase your shutter speed to 250 and increase iso to balance the exposure.

Like others said, it is your shutter speed. If you have the kit lens, then you'll want 1/50s or faster. You'll have to increase your ISO to compensate. You can also try to turn on the VR switch to stabilize your shot.

Firstly the minimum shutter speed to stop motion is around 1/125, I mostly shoot fashion spreads at 1/160 if there's movement involved. A shutter speed of 1/30 is fine if you have steady hands and the subject is not in motion.

I see you had your camera at 6400 iso which is high and should help you get more shutter speed out of your camera for low lit conditions. If when maxing the ISO and you still can't get a good shot, its probably best to purchase a lens that can provide a lower aperture, like a 50mm lens at 1.8 although a good lens with 2.8 can do the trick it is by far more expensive than a prime 50 mm nikon lens.

Edit: Also iI would add you should set your focus point on the middle red dot only. This way you focus on what you want, the photo you took was focused on the background instead of the subject.

So in short the lower the aperture of a lens the more light it will take in and easier it will be to take unblurry photos in low light without the use of a flash, the only downside is your depth of field will not be as great.