Essentially, you have a conflict of interest. A manager's job is to meet deadlines. A scrum master's job is to ensure estimates are as accurate as possible and to work at a sustainable pace. A manager tends to want more work pulled into a sprint, and a scrum master tends to want less. Although a good manager can balance that conflict, it's much easier when the job is split between two people. Managers usually are much better suited for the product owner role.

There's nothing wrong with acting as scrum master if no one on your team is familiar with it, but your team will see benefits if you hand off that role after a few months. It's important for that role to be seen as a peer. Even non-management scrum masters often have to rotate out after a while because the team starts to treat them too much like a manager.

Essentially, you have a conflict of interest. A manager's job is to meet deadlines. A scrum master's job is to ensure estimates are as accurate as possible and to work at a sustainable pace. A manager tends to want more work pulled into a sprint, and a scrum master tends to want an amount that can be realistically finished, regardless of external deadlines. Although a good manager can balance that conflict, it's much easier when the job is split between two people. Managers usually are much better suited for the product owner role.

There's nothing wrong with acting as scrum master if no one on your team is familiar with it, but your team will see benefits if you hand off that role after a few months. It's important for that role to be seen as a peer. Even non-management scrum masters often have to rotate out after a while because the team starts to treat them too much like a manager.