I would say a good excel sheet is an easy and solid method to get your vocabulary organised. But if you want to look into more specialised software I have found the following programs:
1. PolyGlot v 2.1
It is free to use and provides everything you need to create your language. It has an integrated lexicon, where you can enter the words. It has also the ability to import from and export to excel, which means you can easily move your already existing work to the program (and back from there into other formats). Have a look at the manual here for how the lexicon works and other features. As a github project it comes also with the source code, so if you know how to code, you can alter the program to your needs.
2. Field Linguist's Toolbox
Well, it is free to use and used by actual linguists. Again, this program is specifically dedicated to maintaining lexical data. From a first glance it might not be as easy to use as PolyGlot though.
3. Lexique Pro
Another free to use program. This is dedicated to displaying and working with your lexicon, but you will need another program to read the data from - like the aforementioned Toolbox.
This program comes with a price tag, but is currently on sale for under 10 $. But it is a language generation program and so might not really suit your needs. After all you have fun with developing your own languages, but I included it for sake of completion.
5. other Software
Under the above link you will find a compilation of other useful software for conlanging.