Phalenopsis flower spike growing from second node only.
 

A month ago I bought a phalenopsis orchid which has a flower spike growing , but now I observe that the spike has started to develop from the second node only and the tip of the spike is not growing . What might be the reason ? Will it grow ?

There are several reasons that could happen.

A change in conditions might have caused the original growth tip to stall, but then when the plant got comfortable again, it resumed from a bit lower.

It might have species in its background that have branched spikes.

Maybe it was treated with a plant growth regulator (doubtful, but possible).

It's certainly nothing to be concerned about.