What is the name of your state?NY
Single with no children and have one sibling. Is it necessary to make a will, or does sibling inherit estate by default?
If, at the time of your death, you have no will and are not survived by a spouse, issue (children, grandchildren, etc.), or either of your parents, and have one surviving sibling and no issue of deceased siblings, then your surviving sibling would inherit your entire estate (after estate debt is paid).
If you want that result, then there is probably no need to make a will.* However, if you want a different result, then it will be necessary to make a will. Depending on the value and nature of your assets (particularly if you own real property), it might be desirable to create a will or trust.
* - Depending on your county of residence, making a will might be desirable to prevent the public administrator from becoming involved in the administration of your estate.