How many candy do you have?
If you have the 200 candies you need then you probably have a different Lapras to power up.
If you don't, then power up the 1927, or just wait to get a better one.
(Basically - hard luck with the level of the 100 iv guy. There's nothing you can do really to power him up - it's simply too many candies. If you only have the 6 candies from two catches, then it's debatable whether the 1927 is worth powering yet. Wait until you have enough candies to get it where you want it, then choose the best one).