Is it appropriate to mention lack of expertise in certain area as limitation for master's thesis? I'm currently finalizing my master's thesis and am working on the discussion and limitations part. 

I did some relatively standard statistical tests on my data, which gave promising results. My supervisor suggested trying some machine learning to create a predictive model. While I did take a basic machine learning course during my master's, I am by no means an expert in this area.

Now, my machine learning model performed pretty okay. But, since I only know some basic machine learning, I'm sure better results might be achieved with other machine learning methods I have not tried due to lack of expertise. Is it appropriate to mention this lack of expertise as a reason why I did not try to further improve these models?

Note: I tried 2 different ML methods/algorithms, which were suggested by another member of staff.
Rather than describing this as a limitation, I would present this as an area for future research. For example, 


  Machine learning methods X and Y produced promising results for predictive modeling. An area for future research would be to optimize these as well as explore methods, a, b, and c.


and then build upon this with details to be an appropriate length (probably a paragraph or two).