Knowing where you live would help a lot in determining when it would be right for you to prune. It's different for different climates. But I don't think this is the right time for hard pruning in most climates. If the tips were eaten off by something just snip off the tip down to the next set of 5 leaves and it should start to grow again.

What seil said - we need to know where you are. In addition - do you have deer? If deer are nibbling it, it will not be able to get any bigger. I have deer, and all of my baby roses go into wire cages until they are large enough to survive a little grazing.

Jackie

I'm in Sri Lanka where the temperature can't ever go any lower than 26 C and no there're no animals in my yard because it's well fenced. The plant looks too young to prune but I'll give it a shot

You don't need to prune it just take off the chewed tips down to just above a leaf set. The plant will start to grow from the leaf set area.