How can i make my chest look less bony?

If you want to gain muscle mass in your chest you have to work your pectoral muscles hard. The basic exercise for this is the bench press. First a cautionary note; you are likely almost done with your period of rapid growth. If that is the case you have to use caution when doing any exercise. Your bones and muscles grow and strengthen faster than the tendons and ligaments that join bone to bone and muscle to bone. Your muscles can be capable of handling more weight than your tendons and ligaments can support. This can lead to injury, and injury that can take many months to heal. So when doing any exercise start slow and build up very gradually. For your chest do the exercise using progressive resistance. It works this way. You do four sets. On the first set experiment until you find a weight that allows you to do 10 reps. Even if you feel you can do 11 reps...don't. Second set: Increase the weight so that you can do only 7 reps. Third set: More weight, enough so that you are limited to 5 reps, no more than that even if you feel you can do another rep. Fourth set: Again more weight that will limit you to 3 reps with good form. When you first start do not allow the bar to touch your chest. This keeps the lower part of your arm parallel with the floor so that you don't over extend the tendons and ligaments in your shoulders. A month into exercising you can allow the weight to lower to your chest. With this type of exercise you are continually challenging your muscles to do more. You will be sore the next day or two at first. This is normal. Gradually increase the weights as you can handle them, but do not increase the reps. You can also do chest flys which will help. If you can incorporate this into your regular workouts, great. Good luck.

Bench press

3 sets

1. Set 8 reps

2. Set 6 reps

3. Set 8 reps

Lift heavy so those last reps are hard as f*ck

Barbell bench press

dumbbell bench

fly's

include bench

decline bench

Do 4 sets of 10 reps with a weight that becomes difficult to get 10 reps on the 3rd and 4th sets.

I presume when you say 'bony chest' you mean that your collarbone sticks out?

This is to be expected, as you are quite underweight given your height. It's good that you're slowly gaining weight, so continue to do that, and eventually you should start to see a difference.