In Jain Dharma, the main harm is not the mere touching of the body, but the inner passion, attachment, and lustful intent behind it.

So, if you are touching your body without any sexual desire, for example to relieve itching or discomfort, it is not usually counted as a very grave sin like brahmacharya-virodh / abrahma caused by lustful conduct.

However, from the Jain path of self-restraint:

• Body attachment should be reduced
• Unnecessary touching should be avoided when possible
• Mind, speech, and action should remain pure
• If it is only for necessity and without passion, the fault is much less

So the simple answer is:

No, if there is no sexual desire or lustful intent, it is not a major grave sin. But Jainism still teaches carefulness, modesty, and detachment from the body.

If you want, I can also explain this according to Shwetambar and Digambar understanding.