Usually it’s fine to leave a toilet clogged overnight, as long as it’s not close to overflowing. In some cases, the extra time may give the clog time to work itself out. For example, if it’s caused by an excess of toilet paper, letting it sit could result in the clog dissolving and you may be able to simply flush it away by the time you wake up.  Only let it sit though if you have more than one toilet in the home.