Uddhav Thackeray, the incumbent Chief Minister of Maharashtra, did not resign from his post. Therefore, there is no new Chief Minister of Maharashtra who has been sworn in after his resignation. As of my knowledge cut-off date of September 2021, Uddhav Thackeray continues to serve as the Chief Minister of Maharashtra.

Uddhav Thackeray is the leader of the Shiv Sena, a regional political party in Maharashtra. He was sworn in as the Chief Minister of Maharashtra on November 28, 2019, following a power-sharing agreement between the Shiv Sena, Nationalist Congress Party (NCP), and Indian National Congress (INC) after the 2019 Maharashtra Legislative Assembly election.

The 2019 Maharashtra Legislative Assembly election saw the Shiv Sena, Bharatiya Janata Party (BJP), NCP, and INC contesting the polls separately. The BJP emerged as the single largest party with 105 seats in the 288-member assembly. The Shiv Sena won 56 seats, while the NCP and INC won 54 and 44 seats, respectively.

However, the Shiv Sena and BJP could not agree on a power-sharing arrangement, and the Shiv Sena eventually broke its alliance with the BJP. The Shiv Sena then formed an alliance with the NCP and INC, and Uddhav Thackeray was sworn in as the Chief Minister.

Since then, the alliance government has faced several challenges, including the COVID-19 pandemic and the controversy surrounding the death of actor Sushant Singh Rajput. However, the government has managed to complete two years in office.

In conclusion, there is no new Chief Minister of Maharashtra who has been sworn in after the resignation of Uddhav Thackeray. Uddhav Thackeray continues to serve as the Chief Minister of Maharashtra, as of my knowledge cut-off date of September 2021.