Hello and welcome. Technically, your share will be regarded as a windfall and will be payable into the IVA. Should they be so minded the creditors could force a sale.
You cannot use a sum of money the creditors are entitled to anyway as a settlement offer.
Under the terms of your IVA you are probably bound to disclose windfalls, failure to do so could fail your IVA, should the IP discover the omission at a later date. At annual review, and / or at final review you will be asked to sign a statement confirming that you have not aqcuired any assets during the IVA.
There is, however, ons straw to grab at ...... you actually acquired this asset prior to the IVA commencing, the fact that it was omitted at that time was because you had no knowledge, so there is a slim chance the IP could deal with it differently. However, you will need to discuss this with your IP.
Might I ask which company you are with, and how did you discover this inheritance ? The first part of the question is to see if your IP is known to us and we can comment on there helpfulness, the second is me being purely nosey

My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014