Welcome to bonsai, and welcome to the forum. I hope that you find this to be a rewarding and long-term hobby.
In addition to what Paul wrote above, I'd say that if you want to thicken the trunk, doing a major chop at this point would be the most counterproductive thing that you could do. There's a lot of science and detail to it, but in general, the way to grow a trunk the fastest is to make sure the tree has plenty of room for lots of roots to grow (either in the ground or in a large pot), give the tree proper sun/water/fertilizer, and give it a few years to grow before you chop anything. If you want a thicker trunk, then you must grow lots of roots and branches first. Limiting or reducing roots/branches at this point will just slow down the thickening of the trunk.
Here's a very informative article on how to thicken trunks:
https://www.evergreengardenworks.com/trunks.htm
One of the common mistakes that people new to bonsai make (and I'm not saying that you're doing this, just saying in general) is that they "love their tree to death." They are so excited about bonsai that they do too much to the tree too fast, and it causes so much stress for the tree that it dies. Make sure that you put just as much, if not more, effort into keeping your tree alive and healthy as you do styling it into a bonsai.
Paul gave very good advice in also getting a few more trees. When a tree is very young like your Japanese maple is, there's only a little bit of "stuff to do" to it per season. If you have 5 trees, for example, your little bit of "stuff to do" multiplies by 5. It would give you a lot more "stuff to do," meaning that you'll get more practice and learn more quickly without loving your tree to death. Home Depot, Lowe's, or garden centers often have good starter trees and shrubs for $10 or less.
Also, if you update your profile to add in your general location, then people can give you advice more specific for your particular location. Keep up your research and never stop learning!