The family of the 62-year-old woman said the nurse's son played a prank on his mother.
California Lottery officials said they were skeptical after a spokesperson for nursing home owner Shlomo Rechnitz said the winner was a senior registered nurse at Park Avenue Health Care and Wellness Center in Pomona.
Rechnitz's spokesperson said the nurse was given a ticket by her boss, who bought 18,000 tickets for his employees and residents at 80 nursing home across California.
Rechnitz described the prank as "despicable" and told ABC News he wants the nurse to have some fun with the situation. He said he will buy an all-expense paid vacation for the nurse and her family to anywhere they choose.
Lottery officials stated that no one has come forward to claim the prize.
The winning ticket was purchased at a 7-Eleven located at 4092 Chino Hills Parkway in Chino Hills. Revelers swarmed the store in celebration Wednesday evening.
MORE: 7-Eleven store owner in Chino Hills receives $1 million check
The final total for the jackpot was $1,586,400,000 with a cash value of $983,500,000, according to the Texas Lottery.
Two other winning tickets were sold in Florida and Tennessee.
Powerball is played in 44 states, plus the District of Columbia, Puerto Rico and the U.S. Virgin Islands. The odds of winning are one in 292.2 million.