What to do? Pls suggest guys

I recently joined an early age startup but that place was nothing what they told it’d be. So I decided to quit in 2 weeks.

I now have an offer from a listed organisation and I am joining on Thursday. However, I haven’t told them about the last 15 days I spent at this startup and have submitted relieving of the last 2 orgs I worked with for 2 yrs each.

Can there be a problem later?