Well the obvious answer was he can sue for recounts, which I accepted as the answer.
But today, election day Donald Trump sued the Clark County elector for letting people in line at closing time still vote. Read details here.
It should be noted that Nevada is a state where Las Vegas and Reno will lean toward the left in an election and the rest of the state is on the right. So if there is a legal strategy here, it is to put into limb the votes in left leaning areas. This particular polling place was at a Latino super market.
In the lawsuit Trump, a New York businessman and reality TV personality who has never previously run for political office, asked that the ballots from that polling place be kept separate from other votes, pending any future legal challenges to the results in the state.
Hanging things up in court, is one of the options.
I would love to hear more options like this, and would like to broaden the question to include this kind of thing. (kind of late I know).