Let it grow. This needs to grow and develop a trunk, or if you want it to be a clump or Grove you need to develop trunks, plural. Keep moving to larger pots. When the current pot is full of roots, move to a pot one or two inches larger in diameter.
At some point, you should choose, and reduce to either a single trunk, or up to 5 trunks. I would look toward a single trunk.
Watch this video, it shows the problem of trying to thicken trunks in pots.
Just sharing my latest video on 10 different ways to thicken your bonsai trunks.
www.bonsainut.com