Is it normal to still have some pain tenderness soreness 12days after appendix removed. sometimes feel like insides burning. healing good tho?

Yes, unless bad: If your symptoms are worsening, it's a bad sign. Hard to know. You have a surgeon though! go to them for follow up!

Sounds normal : If you had an inflammed appendix removed, there can be residual inflammation that can cause occasionally cause some discomfort for several weeks. However, it should gradually resolve getting less every day or every few days until totally resolved. If it doesn't resolve soon, you should see your surgeon.