Stock Sale & Estimated Tax Penalty

Hello.  I sold stock from my brokerage account in 2019.  The brokerage firm did not withhold taxes.  Am I at risk of any penalties for not finding a way to pay the estimated tax on this sale during 2019?  If so, is there anything I can do now (before all tax forms are distributed in 2020 for 2019 tax filing) to address this situation?  Please advise.