Can a personal injury attorney deny sending me my settlement money if it's in his trust fund and I decide not to file a suit?

No.  Under the Nevada Rules of Professional Conduct 1.15(d), an attorney is required to promptly remit to you settlement monies. (d) Upon receiving funds or other property in which a client or third person has an interest, a lawyer shall promptly notify the client or third person. Except as stated in this Rule or otherwise permitted by law or by agreement with the client, a lawyer shall promptly deliver to the client or third person any funds or other property that the client or third person is entitled to receive and, upon request by the client or third person, shall promptly render a full accounting regarding such property. Many times a dispute arises between the attorney and client over the appropriate fees to be collected and charged, at which time the Attorney will hold the monies in trust pending a resolution of the dispute.