A Shiva Lingam dream can have the following three meanings:

Usually if any God appears in our dreams, it means that their temple should be initiated nearby.

1

Other meaning of dreaming about a Shiva Lingam means that something bad that was coming your way has been removed. Since he swallowed the poison, similarly, he swallowed your problems.

2

Third meaning of the similar dream is that you might need to go out, find a nearby Shiva temple and bathe the Shiva Lingam with milk.

3

Every dream can have various meanings. It depends upon which  one suits you the best.