Feeling lower back pain and heaviness as you described is suggestive of lumbar muscle spasm or strain . It's because of excessive use of those muscle or sudden jerky movements such as bending twisting or turning . This will resolve slowly . You need to give your muscle rest.you can apply topical painkiller ointment. Do some extension exercises . And avoid excessive bending and jerking etc. If pain persists for longer duration consult an orthopaedic surgeon .