The dev team can add small tasks needed to accomplish the Sprint Goal to the Sprint Backlog
Here is what the Scrum Guide has to say on this topic:
The Development Team modifies the Sprint Backlog throughout the
Sprint, and the Sprint Backlog emerges during the Sprint. This
emergence occurs as the Development Team works through the plan and
learns more about the work needed to achieve the Sprint Goal.
As new work is required, the Development Team adds it to the Sprint
Backlog. As work is performed or completed, the estimated remaining
work is updated. When elements of the plan are deemed unnecessary,
they are removed. Only the Development Team can change its Sprint
Backlog during a Sprint.
If these small tasks are needed to accomplish the Sprint Goal, the dev team can add either sub-tasks or separate stories to the Sprint Backlog and complete them during the sprint.
However, if they are not strictly required to accomplish the Sprint Goal or new larger stories are discovered, write them up as separate stories and park them in the Product Backlog for the PO to prioritize.