I have a question about the picture of you holding the finished bootie. What is that little bit of yarn hanging out at the back of the heel? Is that where you finished or began sewing? Either way, you don't want to have a little short piece of yarn sticking out like that. I'm hoping this is not where you finished sewing and you just cut the yarn off when you finished. If you did that the sewing will come undone. :-( At both the beginning and end of the sewing you need to leave a tail of yarn about 6 inches long and work that tail in on the inside where it won't show for over 1" to up to 2 inches. That way the sewing won't come undone. Any other ends, from making the bootie need to be treated the same way so the knitting doesn't come undone.
Here is some info about hiding in the tails. LINK
This says how to hide them in a seam, which is not the only way, but you can use this for at least some of your ends. Here is another way called skimming. LINK
There are other ways, but this should do you for now.
You bootie looks real nice. Very nice for your first bootie. You learned a lot.