If you make over $400 in income from book sales you need to take that income and apply self-employment tax on that income.

In addition you need to make quarterly payments for the estimated tax.

If you haven't done so yet. To fix your situation you can file an amended return. A CPA can do it for you... given your income, you should be able to afford it.

As your income grows so it does the likeliness of being audited.

https://www.irs.gov/businesses/small-businesses-self-employe...

Now that you have published your story, your real name and the income you obtained I strongly suggest to do it ASAP.