Your tree is looking nice and healthy. When you go to transplant re pot the tree at the same soil depth you have now. Eventually the pit will dry and decompose. Do not try to remove the pit as you may cause damage to the roots and this is a valuable supply of nutrients that the roots will slowly absorb. 
I have also provided you with a link for future care of your tree.
Enjoy.
http://www.californiaavocado.com/how-tos/your-own-avocado-tree

 Thanks, Wendy. I think the split in the pit is drying out the roots so I may put a little soil in it and repot at the same depth. Keep your fingers crossed. This is a pit from a  Puerto Rican avocado! I have another avocado plant that's American grocery store which is far larger and I did cover that pit with soil many months ago  and it's doing OK . Thanks again!

Sounds like a fun adventure. Enjoy looking at the similarities and differences as they grow.
Its normally ok if you cover the pit. When is partially uncovered it decomposes more slowly. Another good suggestion is use a potting soil with some compost as the trees get larger. That way the soil can provide the needed nutrients versus using fertilizers.