SQL Server shrink log after full and log backup
You should be ok, transaction log backup will allow a point in time recovery. You can shrink the tlog file without any issues. Since you already took the tlog backup with truncate, the log space should be empty (unless there's something like replication, log shipping, etc) and you should be able to shrink the tlog. 

After that, you can continue with your normal schedule of full backup and tlog backups. 

The only situation when tlog shrink is not recommended is when you already know the tlog will grow due the "normal" activity of your database. But from what you said, it should be ok to shrink it.