Hi Do you know where this William was born? If it was in Laxton I might be able to help as I have a list of baptisms of Pinders in Laxton.If he married in 1821, I am assumming a birth c1800 or before. Found: William, bap either 13 or 10 April 1794 to William and Mary Pinder.
Before that, my transcription has a gap (between 1786 - Mar 1792) but also found: William bap 24 Oct 1778 to Thos. and Susannah Pinder; and William bap 19 Aug 1781 to Robt and Dorothy Pinder.
I don't have a marriage for William but, as you say, he married in Nottingham and I only have just Laxton.