A programming language is a tool for solving problems, but different languages often lend themselves to different kinds of problems. For example, Java is a good language if you want to create an Android app, whereas Python is a good language for writing automation scripts. The 'C' language is often used to work with embedded/hardware devices, etc.
The best thing to do is to think of something which interests you, and think of a project to work on, so if you were to write some kind of app, perhaps it'd be related to something else in your life - for example, if you or a friend/family happens to be working in a job where you could use a language to automate some repetitive part of that job, or maybe create some kind of app to help manage data for that job.
If you don't have any ideas, consider working in an open-source project using the language of your choice - this is a really great way to get yourself some real-world experience solving problems, looking at and debugging existing code, likely also needing to work alongside other programmers who are also working on that open source project. Have a look at
http://www.firsttimersonly.com/Lastly, learning a programming language isn't really the end, it's just the beginning. When you reach a point where you're comfortable in one programming language, you'll find that you have thousands of other things to learn about, including how to design and structure your code, how to "think" in terms of Object-Orientation, how to analyse and break down complex problems to turn them into something you can solve with a computer, and then how to use all kinds of tools and libraries which might help you do things like create a GUI, a web server, work with a database, draw some graphics, handle sound, communicate with other apps/devices over a network, etc.