Picture gets blurry when zooming in

I can focus on extremely close

The closest focus a Nikon 18-55 should work at is about 25cm - that's about 10 inches.

If you can focus much closer than that it is a fault. It likely needs to be repaired or replaced.

Before going down that route try a factory reset on the off chance it is an odd computer issue (which seems unlikely, but these gadgets are quite complex computers now).

My Nikon 3400's kit lens(18-55mm) works fine when I take pictures at 18mm. But when I extend lens beyond that, the picture gets blurry(no clarity)

Again this suggests (to me) a physical fault with the lens.

It all started after I tried to shoot in extremely low light condition.

I cannot see how that would cause a problem. It could be a coincidence and the fault would have developed anyway.