Generally speaking,
The flatness of the test specimen’s loading surface shall be within 0.05 % of its diameter.
(Preparation of Test Specimens for Concrete Strength Testing—JIS A 1132:2020)
There is a standard called...
Therefore, please cap or polish the surface as much as possible.
If this is not done, strength variations are likely to occur, and in some cases, the required strength may not be achieved due to uneven loading.