There is something called a tongue-thrust reflex that babies 4-6months can develop. It looks like they are chewing their tongues but instead, they are showing readiness for solid foods. It's a reflex that helps them push out solid food to avoid choking. So please, it is too early to determine "bad habits" in a child as a lot of the things they do, aid their development, you can keep watch for a few more months, the phase will pass.

Tongue sucking is one of the common oral habits seen among children. It is normal for infants to suck their tongue, thumbs or fingers. It gives them a form of comfort or emotional security but when this habit goes beyond the age of 5 years when the permanent teeth start to erupt, then it can cause dental problems such as the teeth being out of alignment. You do not need to worry or do anything for now. As the baby grows older you will need to encourage him or her to stop by positive reinforcement that is giving rewards on days when the child does not suck. I hope you find this very useful.