Lo siento, aún no me he puesto a hacerlo.

This keeps tripping me up, but ponerse a hacer means to start something. See definition 27 on this page: http://www.spanishdict.com/translate/ponerse (or search for “ponerse a hacer” on the page in case they edit the order).

Doesn’t it mean the same thing in this context? That’s how I understand it, anyway.